Issue with f2py in Numpy 1.13 when character arrays appear in a callback function

There is an issue with f2py in Numpy 1.13 when character arrays appear in a callback function. The following example works with Numpy 1.12 but not in 1.13:

#! /usr/bin/env python

from __future__ import print_function
import numpy
from subprocess import call

#
# build extension from FORTRAN source
#
source = """
       subroutine func_with_callback(callBack, cu, lencu)

       implicit none

       integer :: lencu
       character*8 cu(lencu)
       external callBack

       print *,'Lencu:', lencu

       print *,'Calling callback...'
       call callBack(cu, lencu)
       print *,'Back in fortran...'

       end subroutine func_with_callback
"""

with open("callback.f", "w") as src_file:
    src_file.write(source)

rc = call("f2py callback.f -m callback -h callback.pyf".split())
if rc: quit()

rc = call("f2py -c callback.pyf callback.f".split())
if rc: quit()


#
# define callback function
#
def callBack(cu, lencu):
    print ('In callback:', cu)

#
# call library function with callback
#
from callback import func_with_callback
print(func_with_callback.__doc__)

print("\nNumpy Version:", numpy.__version__, "\n")

cu = numpy.zeros((1, 8), 'c')

func_with_callback(callBack, cu)

================

Numpy Version: 1.12.1

Lencu: 1
Calling callback...
In callback: [['' '' '' '' '' '' '' '']]
Back in fortran...

================

Numpy Version: 1.13.3

Lencu: 1
Calling callback...
Call-back cb_callback_in_func_with_callback__user__routines failed.
Traceback (most recent call last):
File "test_callback.py", line 57, in
func_with_callback(callBack, cu)
ValueError: data type must provide an itemsize

The problem came in with a618b4e, #8948.

The proximate cause is this code in the generated source:

  if (cb_callBack_in_func_with_callback__user__routines_nofargs>capi_i) {
    PyArrayObject *tmp_arr = (PyArrayObject *)PyArray_New(&PyArray_Type,2,cu_Dims,NPY_STRING,NULL,(char*)cu,0,NPY_ARRAY_CARRAY,NULL); /*XXX: Hmm, what will destroy this array??? */

BUG: Fix f2py string variables in callbacks.

TST: Test f2py passing string array to callback.

I've recently come across this issue while using f2py in numpy 1.20.3. As a minimum working example, I have the following simple fortran module which declares two allocatable arrays (charge is real type and names is character). The subroutine "main" will allocate them:

! -*- f90 -*-

      module inputs
      implicit none
              real*8, dimension(:,:), target, allocatable :: charge
              integer is_alloc
              character(len=10), allocatable, dimension(:) :: names
      end module inputs

      subroutine main(N)
      use inputs
      implicit none

      integer ii, jj, N
      
      IF (allocated(charge)) THEN
         deallocate(charge)
      end if
      allocate(charge(N, N))
      allocate(character(len=10) :: names(N)) !, source="TEST")

      END subroutine

I can build this by running python setup.py build_ext --inplace with the following setup.py file (having put the above code in test.f90):

from numpy.distutils.core import Extension
from numpy.distutils.core import setup
from numpy.distutils.misc_util import Configuration


F90_COMBINED = "test.f90"

calc_ext = Extension(
    name="alloc",
    sources=[F90_COMBINED],
    include_dirs=['.'],
    libraries=['gsl', 'gslcblas'],
    extra_f90_compile_args=['-Wargument-mismatch'],
)

def configuration(parent_package='', top_path=None):

    config = Configuration('', parent_package, top_path,
                           ext_modules=[calc_ext])
    return config

if __name__ == "__main__":
    setup(configuration=configuration)

This builds a module called alloc. Here's a screencap of what happens if I try to access each allocated array.

Any suggestions would be greatly appreciated!

Note that the original issue of callbacks and character arrays is fixed by #19388. The issue raised for allocations is still relevant and tracked separately.

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Issue with f2py in Numpy 1.13 when character arrays appear in a callback function #10027

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Issue with f2py in Numpy 1.13 when character arrays appear in a callback function #10027

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charris commented on Nov 15, 2017

charris commented on Nov 15, 2017

aelanman commented on Dec 8, 2021

HaoZeke commented on Jun 5, 2022

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